Rivers Revision
River Erosion and resulting landforms
The 4 main processes of river erosion are hydraulic power, attrition, corrasion
and corrosion.
Most river erosion takes place in the uppr course of the river
Features formed by river erosion are waterfalls and gorges and v shaped
valleys, found in the upper course.
Processes of river transport
Materials are transported by 4 main processes – traction, saltation, solution
and suspensions.
River deposition and resulting landforms
Most deposition takes place in the lower course
Features formed by deposition include flood plains, deltas, and levees.
Meanders and ox bow lakes are formed as a result of both erosion and
deposition
The valley cross-section changes to a broad U shape in the lower course
Overall the long profile of a river is smooth and concave with a steep gradient
at the source which decreases to almost nil near the river mouth.
Key words and definitions
Erosion
Transportation
H
T
A
S
A
S
S
S
Deposition
Landforms
Erosion
Deposition
Erosion and Deposition
River Basins
Rivers begin in upland areas and flow downhill, becoming wider and deeper
until they enter the sea.
It is subdivided into 3 sections
The upper course
The middle course
The lower course
D
E
B
C
A
F
A=
B=
C=
D=
E=
F=
Tributary
Confluence
Mouth
Watershed
Source
Drainage basin
…………………: where two rivers meet
…………………: the area drained by a river and its tributaries
…………………: where a river flows into the sea
…………………: where the river begins
…………………: a smaller river which flows into a larger river
…………………: the imaginary line surrounding a drainage basin
The upper course of a river
Waterfalls
Write a paragraph to explain how waterfalls are formed………..
The middle course of a river
As the river flows downstream the gradient becomes less steep. Sideways
erosion becomes more important than vertical erosion and the river starts to
meander. Some of the rivers energy is also used to transport material
downstream.
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Meanders
Write a paragraph to explain how meanders are formed………….
The lower course of a river
As the river gets nearer the sea deposition becomes the most important
process, encouraged by:
A large load carried by the river
Any obstruction e.g. lake
Any fall in the volume or loss in the velocity
Features of the channel in lower course
Wide
Deep
Lined with sand and mud
Islands of silt
Carries large load of alluvium
Feature of the valley in the lower course
Wide flat flood plain
Levees found on river banks
Ox bow lakes and meander scars
A line of river cliffs found at the edge of flood plain.
Make sure you can
label the features
highlighted in black onto
the flood plain diagram.
Ox- Bow Lakes
Using the above boxes use and label diagrams to show the formation of an
ox-bow lake. Use the boxes to give a brief explanation.
Write a few sentences to explain how flood plains are formed…..
Levees.
Explain the formation of a Levee……………………..
Describe the physical features of a Delta………………………………..
Flooding
Flooding is a normal occurrence in the lower course of a river. It occurs when
the river overflows its banks and leaves the channel. River flooding helps to
form several river features: Flood plains, ox-bow lakes and levees.
Causes of flooding:
Natural:
Long continuous rainfall
Cloud-burst in thunderstorm
Rapid melting snow and ice
Human:
Expanding urban areas
Deforestation
Occasional disasters e.g dam burst
Name your case study!!!